WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.1N 147.1E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 351 NM NORTHEAST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS
OF DEEP CONVECTION TIGHTLY WRAPPING INTO THE LOW-LEVEL CIRCULATION
CENTER (LLCC) OF TROPICAL STORM (TS) 04W (MUN). THE SYSTEM IS
COMPACT, WITH CONVECTION MAINLY SPREAD ACROSS THE SOUTHERN
SEMICIRCLE. ENVIRONMENTAL ANALYSIS REVEALS CLOUD TOP TEMPERATURES
BETWEEN -62 AND -72 DEGREES C. ADDITIONALLY, TS 04W IS IN OVERALL
FAVORABLE CONDITIONS FOR FURTHER INTENSIFICATION, AS INDICATED BY
WARM (27-28 C) SEA SURFACE TEMPERATURES (SST), LOW (10-15 KTS)
VERTICAL WIND SHEAR (VWS) AND MODERATE OUTFLOW ALOFT. THE CORE OF THE 
SYSTEM REMAINS MOIST, HOWEVER SIGNIFICANTLY DRIER AIR IS SURROUNDING 
THE CIRCULATION AND IS EXPECTED TO BEGIN IMPACTING THE STRUCTURE OF 
THE 
VORTEX. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE ANIMATED VISIBLE SATELLITE IMAGERY SHOWING A PARTIALLY EXPOSED 
LLCC 
IN THE CENTER OF THE ASSOCIATED DEEP CONVECTIVE BANDING. THE INITIAL 
INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE 
AGENCY DVORAK AND OBJECTIVE ESTIMATES LISTED BELOW, IN CONJUNCTION 
WITH 
THE COMPACT STRUCTURE OF THE SYSTEM.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH
AND SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 56 KTS AT 050312Z
   CIMSS ADT: 41 KTS AT 050530Z
   CIMSS AIDT: 56 KTS AT 050530Z
   CIMSS D-MINT: 45 KTS AT 050312Z
   CIMSS D-PRINT: 41 KTS AT 050600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR SURROUNDING THE SYSTEM

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 04W IS FORECAST TO TRACK EAST-NORTHEASTWARD
OVER THE NEXT 24-36 HOURS, UNDER THE PREDOMINANT INFLUENCE OF A STR
TO THE SOUTH. AFTERWARD, RIDGING WILL BUILD TO THE EAST, RESULTING IN 
STEERING THE SYSTEM NORTHWESTWARD AND EVENTUALLY NORTHEASTWARD. IN 
TERMS OF INTENSITY, TS 04W IS FORECAST TO REACH PEAK INTENSITY OF 60-
65 
KTS WITHIN THE NEXT 12-24 HOURS. AFTER THAT, RAPIDLY COOLING SST, AS 
WELL AS INCREASING DRY AIR ENTRAINMENT WILL RESULTS IN WEAKENING. 
AROUND TAU 72, THE SYSTEM WILL BEGIN ITS SUBTROPICAL TRANSITION, WHICH 
IS EXPECTED TO BE COMPLETED BY OR BEFORE THE END OF THE CURRENT 
FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN FAIR
AGREEMENT, WITH CROSS-TRACK SPREAD OF JUST 25 NM AT TAU 36,
EXPANDING HOWEVER TO OVER 250 AT TAU 72, INDICATING UNCERTAINTY IN
HOW DIFFERENT MODELS IDENTIFY THE INTERACTION BETWEEN THE SYSTEM
AND THE BUILDING RIDGE TO THE EAST, AS WELL AS THE BAROCLINIC ZONE
TO THE NORTH. ALONG-TRACK SPREAD AT TAU 96 IS OVER 900 NM, AS SOME
MODELS INDICATE DISSIPATION PRIOR TO THE COMPLETION OF THE
SUBTROPICAL TRANSITION. INTENSITY GUIDANCE IS IN GOOD AGREEMENT,
WITH ALL CONSENSUS MEMBERS FORECASTING SLIGHT INTENSIFICATION OVER
THE NEXT 12-24 HOURS, FOLLOWED BY CONSISTENT WEAKENING AFTERWARDS.
UNCERTAINTY INCREASES TOWARD THE END OF THE FORECAST PERIOD, AS
SOME HAFS PROJECTS DISSIPATION AS EARLY AS TAU 60, WHILE GFS REMAINS 
ABOVE WARNING CRITERIA AT LEAST THROUGH TAU 84.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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